The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Internal combustion engines including compression-ignition engines use fuel that originates from raw stocks including petroleum, referred to as petrodiesel fuel, and raw stocks including biological sources, referred to as biodiesel fuel. Fuel suppliers may provide fuels that have varying mixes and blends of petrodiesel fuel and biodiesel fuel.
Petrodiesel fuel originates from the fractional distillation of crude oil and is a mixture of carbon chains that typically contain between 8 and 21 carbon atoms per molecule. It is known that biodiesel fuel refers to a vegetable oil-based or animal fat-based diesel fuel consisting of long-chain alkyl (i.e., methyl, propyl, or ethyl) esters. Suitable vegetable oil-based feedstocks include soy, rapeseed, and jatropha. Biodiesel fuel may be made by chemically reacting lipids (e.g. vegetable oil, animal fat) with an alcohol.
Fuel may be characterized in terms of a lower heating value (QLHV), which is a chemical energy content of the fuel per unit mass. It is known that different fuels and fuel blends have different heating values (QLHV) and stoichiometric air/fuel ratios, which may affect engine operation and engine performance. A stoichiometric air/fuel ratio is a mixture of air and fuel that has a ratio, measured in mass/mass or other suitable measurement that is sufficient to achieve complete combustion of the fuel and no more.
Known biodiesel fuels have a stoichiometric air/fuel ratio of around 12.46:1 and known petrodiesel fuels have a stoichiometric air/fuel ratio of around 14.5:1. Known biodiesel fuels have densities around 0.8857 kg/L and known petrodiesel fuels have densities around 0.8474 kg/L. Known biodiesel fuels have heating values (QLHV) of the fuel around 37.277 MJ/kg and known petrodiesel fuels have heating values (QLHV) around 42.74 MJ/kg. Known biodiesel fuels have oxygen contents around 11.75% by weight and known petrodiesel fuels have no oxygen content. Cetane numbers for biodiesel fuels may vary from that associated with known petrodiesel fuels.
Known fuel injectors for internal combustion engines inject fuel in response to a command. A command to a fuel injector is in the form of a pulsewidth, i.e., an open time. Thus an injector delivers an amount of fuel that correlates to the open time and fuel pressure, with the amount of fuel measured in volume, e.g. milliliters, which corresponds to a mass of fuel when the density of the fuel is known and the injector is operating as intended.